Deep well pump



Nov. 1, 1949. A. s. soBERG DEEP WELL PUMP Fileduune 28, 1946 Patented Novi l, I

uiTEusTATEs PATENT cerca DEEP WELL PUMP Arnold S. Soberg, Maywood, Ill., assignor. by

direct and mesnc assignments, to Sochris Dcvclopment Company, Chlcagolll., a. corporation of Illinois Application June 28, 1946, Serial No. 680,295

l 21 Claims. 1

My invention relates to pumps and is herein specifically illustrated as a deep well pump, `although the principles upon which this specific disclosure is based are equally applicable to other types of pumping apparatus.

There have been various attempts made in' the past to design a pump which would efliciently convey liquids against high head pressures from a point of liquid supply remote from a convenlent power source to another point for use or storage without the necessity of troublesome or expensive mechanical or electrical connections between the liquid supply and power source, This problem is well illustrated in the pumping of liquids, such as petroleum or water from deep wells. which often deviate from the vertical and reach substantial depths rendering undesirable the use of liftingr rods. Transmission of power to a pump adjacent the liquid supply by hydraulic orpneumatic means has been proposed but, in general, such devices have proven to be sufliciently .complicated and costly to justify only limited use in special circumstances.

One of the primary objects of my invention is to obviate these and other similar problems by providing a simple and inexpensive pump apparatus suitable for use in deep wells wherein the power means may be conveniently disposed at any desired location either adjacent to or remote from the liquid supply without introducing complicated apparatus, which eliminates the necessity of employing rigid lifting rods and which is capable of operation Without attention over extended periods of time on substantially all liquids.

Other important objectives include the provision of pump apparatus of the type described adapted for use in existing wells which incorporate a minimum number of moving parts and which may be manufactured at low cost.

In general these and other objects of my invention are accomplished by disposing in a suit- Y able pump cylinder in or near the liquid supply a hollow piston adapted to be reciprocated by variation of the static pressure of the lliquid column above the piston, which may be effected by a suitable power piston disposed at a remote point but in communication with the liquid column. Downward movement of the hollow piston is produced by an increase in pressure in the liquid above the hollow piston and acts to drive liquid trapped in the pump cylinder by valves into the hollow piston, compressing a body of gas trapped therein. As the pressure on the liquid above the piston is then decreased, the piston rises under the influence of a suitable (Cl. ID3- 44) 2 spring discharging the liquid in the piston into the liquid column. On the next compression stroke of the power piston, a portion of the stroke again lowers the hollow' piston, repeating the cycle, while the remainder of the stroke of the power piston forces liquid from the liquid column to a point of storage or use.

For a more complete explanation of the construction and operation of my device and modifications thereof, reference is made to the following specication and to the drawings in which Figure 1 is a diagrammatic vertical section showing the arrangement of parts of my pumping apparatus;

Figure 2 is a vertical section through a piston;

Figure 3 is a vertical section through a modied form of piston;v

Figure 4 is a diagrammatic vertical section of 4 a modiiied form of my invention; and

Figure 5 is a top view of a pump cylinder taken along the lines 5 5 of Figure 4.

Figure 1 illustrates diagrammatically a. simple form of my pumping apparatus as applied to deep wells having a casing II extending from the surface of the ground downwardly to a liquid supply. The casing is preferably formed of metal pipes having joints presenting a smooth internal surface, the bottom section of the casing being ground and polished to form a pump cylinder l2 preferably of corrosion-resistant metal such as brass, bronze or stainless steel, which may be threaded at its lower extremity to receive a perforated metal well point I3 adapted to admit liquid to the cylinder l2 and trap sand or other debris which would otherwise tend to enter.

The lower extremity of the cylinder l2 is provided with a lateral partition ld having an opening l5' extending therethrough in which is secured, as by threads, a cylinder inlet check valve i6. It should be understood that a check valve as used herein means an irreversible type of valve which will automatically permit the flow of liquid in one direction but will seat automatically to prevent reverse flow. The valve I6 is of this vspring characteristics.

the lower surface of the hollow piston Il to permit the entry of water from the cylinder I2 Into the piston as the piston I8 is forced downwardly. A piston outlet check valve 22 similar in form to the cylinder inlet check valve I8 is secured as by threads in an opening in the upper surface of the hollow piston Il permitting the discharge of liquid from within the piston to the liquid column in the casing II. A tube 23, attached to the piston I8, may. extend downwardly fromvthe piston outlet valve 22 terminating within the piston at a point above the piston inlet valve 2| thereby forming a gas trap in the upper portion of the piston I8, the length of the trap being determined by the length of the tube 23.

Resilient means 24. as for example one or more springs, may be attached to the bottomdof the piston I8 and act against the partition' I4 to force the piston I8 upwardly after compression. Cylinders containing a compressible gas can be substituted for the springs if desired, but I have found that theuse of a plurality of concentric springs is preferable since by employing springs of varying characteristics, a single set of springs becomes applicable to a great number of wells of varying depths. The expedient of utilizing a compressible gas as the resilient means instead of one or more springs is disclosed and claimed in my copending application Serial No. 100,900, series of: 1948, filed June 23, 1949. The strength of the resilient means must be suicient to normally support the piston I8 against the static head of the liquid and of suicient length and strength to return -the piston after compression to such position. Methods of calculating and obtaining the desired stroke and force are known, as are the methods of calculating compound In general, springs of standard design, preferably formed of corrosionresistant material, are suitable for this use.

The top of the casing II is provided with an access hatch 26- sufiiciently large to permit the removal of the piston or other component parts from the well for repair or adjustment when necessary. Bolts 21, or other suitable means, may

be employed to secure the hatch to the casing in such manner as to prevent the entrance or existence of liquid or gas. One or more air bleed valves 28, which may be either manual or automatic in operation may be attached to suitable high points in the system as, for example, to the access hatch 26 to permit the elimination of air from the casing or other points where it might be trapped.

A priming valve 29 connected to a suitable liquid supply may also be attached to the access hatch 26 to permit the introduction of liquid into. the casing for priming the pump. A pipe 3l, of any desired length, communicating with the casing II is connected to means for alternately increasing and decreasing the pressure of the liquid column in the casing I I against the hollow piston I8. For example, the desired change in static pressure can be produced by a power piston 32 operating in a cylinder 33 connected to the pipe 3l and having a piston rod 34 connected to a suitable source of power. Other means, however, such as a diaphragm, may be substituted for the piston and driven in any desired manner. A discharge pipe 36, of any desired length, is also connected to the casing II and serves to conduct the liquid forced upwardlyvby the pump to the point of storage or discharge. A casing discharge check valve 31 is disposed in the discharge pipe adjacent the casing and is preferably adiustably preloaded by a spring 3L In operation, the cylinder I2 and the hollow piston Il are disposed in the bottom of the well adjacent to or preferably below the level of the liquid supply and, if necessary, the casing II is filled with liquid through the priming valve 29. All air in the system below the discharge valve 31 is exhausted through the air bleed valve 28. preferably before power is applied to the piston 32 through the rod 34. As the piston 32 moves for- Ward, liquid within the cylinder 33 is forced through the pipe 3l into the casing II thereby driving the hollow piston I8 downwardly against the pressure of the spring 24. Thisseals the piston outlet valve 22 and the cylinder inlet valve I8 thereby forcing liquid from the pump cylinder I2 upwardly through the piston inlet valve 2l into the hollow piston I8. compressing the gas trapped therein. Downward movement of the piston I8 will continue until the pressure exerted by the body of gas within the piston and by the spring 24 on the liquid above the piston is sufficient to force discharge valve 31 to open. The continued forward stroke of the power piston 32 will then drive liquid from the casing II through the discharge pipe 3 until the forward stroke of the piston 32 has been completed.

As the piston 32 starts its rearward stroke, the discharge valve 31 and piston inlet valve 2I closes, and as the pressure on the liquid column in the casing II is decreased, the hollow piston I8 will rise under the influence of the spring 24. When the pressure of the liquid column in the casing I I is exceeded by the pressure of the liquid within the hollow piston I8, the outlet valve 22 will open, and the liquid within the piston will be forced through the tube 23 and the outlet valve 22 into the liquid column. Travel of the piston I8 is limited by the displacement of the power piston 32, the pressure of the liquid column in the casing II and, if desired, by the spring 24 which may be secured in some instances to the partition I4. As the piston I8 moves upwardly, a vacuum is created in the cylinder I2 below the piston causing the cylinder inlet valve I6 to open and fill the cylinder I2 below the piston I8 with liquid. Continued reciprocation of the piston 32 repeats the above described cycle.

It is obvious that ordinarily means should be employed to separate the liquid and the gas in the hollow piston I8 since in most instances it will be found that the gas is at least partially soluble in the liquid and would therefore be eventually exhausted, causing interruption of operation. In some instances it is possible to employ liquid separating means insoluble in the liquid and having a lower specific gravity and also presenting a barrier to the gas. In other instances it may be found that the liquid is naturally saturated with a gas such as carbon ydioxide and therefore if carbon dioxide is charged to the hollow piston I8, no separating means is required. Generally, however, I may employ a floating piston 38 reciprocably mounted within the hollow piston I8,

having a suitable opening to receive the tube 23 and provided with suitable washers 40 contacting the inner wall of the piston I8 and the tube 23 to effectively prevent the ow of liquid or gas. When the piston 38'is employed, stops 39 may be attached to the lower inner surface of the hollow piston I8 to limit the downward travel of the floating piston 38 to a', point above the lower end of tube 23 thereby preventing loss of gas into the liquid column. Where the required movement is not excessive a rubber diaphragm, at-

tached to the tube 23 and piston I8, may be subupper face of the piston I8 and communicating with the interior thereof is provided for this purpose. As the compressed gas is introduced, the oating piston 38 will be driven downwardly against the stops 39 thereby effectively sealing the gas within the piston.

In some instances diiiculty may be encountered with liquid seeping past the lloating piston 38. If this occurs, a container 4I may be attached within the body of gas, as for example to the upper inner surface of the piston I8, and a quantity of suitable chemical placed therein. The chemical is selected to react with the liquid being pumped to generate gas, thereby renewing the partially exhausted gas supply within the piston. When water is the liquid being pumped, calcium carbide forms a suitable material since as the liquid contacts the chemical, acetylene will be generated. l

From the foregoing it will be noted that this device may be termed a single action pump inasmuch as only one side of the power piston 32 is operative to produce pumping action. It is obvious, however, that the other side of the piston 32 may be employed by suitable connection to another well and the same power pisto-n employed to operate a plurality7 of wells. If a power piston and cylinder of large displacement is available, several wells may be connected by suitable manifold pipes similar to pipe 3l and operated simultaneously, as for example, where the liquid sup?X ply in any one well is sufciently limited to justify the use of the apparatus described.

I have illustrated in Figure 2 modified form of hollow piston I8 employing a resilient bladder to contain the gas. In this modification I prefer to employ a perforated tube 42 extending from the piston outlet valve 22 to the piston inlet valve 2|. A bladder 43 of resilient material such as rubber is fitted into the cylindrical space defined by the tube 42 and the inner surface of the piston I8. A valve 44 extends through the upper surface of piston I8 and communicates with the interior of the bladder 43 to permit charging of the bladder with compressed gas prior to insertion in the well or cylinder. The bladder may be formed, for example, of natural or synthetic rubber suitably treated, if desired, to increase its resistance to the passage of air or solution in the liquid being pumped. In most instances synthetic rubber of the butyl type is satisfactory.

When the pressures selected are relatively high, as will'be the case in deep wells, fabric or other similar reinforcing may be employed in the construction of the bladder 43. It should be understood that the purpose of the perforated tube 42 is to prevent the deformation of the bladder 43 in such manner as to possibly seal the piston outlet valve 22 and therefore if the bladder itself is of such construction as to prevent this possibility, the tube 42 may be eliminated. In most instances, however, its use is preferable since it simplies the design and construction of the bladder 43.

When the hollow piston I8 is formed in the above described manner, its operation is substantially identical t0 that previously described except that liquid entering the piston during its downward stroke passes through the piston inlet valve 2| and through the perforations in the tube 42 to compress the gas in the bladder 43. On the upward stroke oi' the piston, the pressure of the gas in the bladder seals the piston' y inlet valve 2I and forces liquid outwardly through the piston outlet valve 22.

Another suitable means of separating the gas in the hollow piston I8 from the liquid is illustrated in Figure 3. Expansible metal bellows 4S shaped as a ring may be telescoped over the tube 23 within the piston I8 and secured in any desired manner at the lower extremity to the tube 23 and the inner walls of the piston, Since they material employed to form the bellows 46 is necessarily relatively thin, it is desirable to prevent contact between the bellows 46 and the walls of the piston I8 or the tube 23. I therefore provide a ring-shaped guide 41 attached to the top of the bellows shaped to bear against the tube 23 and the piston I8 and may, if necessary, provide additional intermediate guides 48 between the guides 41 and the base of the bellows 46 to maintain the bellows in the desired position. Preferably the intermediate guides 48 are provided with laterally extending flanges 49 on the irmer or outer edges to limit the downward travel of the head guides 41 thereby preventing complete collapse of the bellows 46 when compressed gas is introduced through valve |40 suitably positioned in the upper surface of the piston I8.

While, as previously mentioned, substantially any form of attachment may be employed to secure the bellows 46 within the piston, welding constitutes a preferred form since the possibility of subsequent leakage is thereby practically eliminated.

Other similar forms of gas containers, as for example sealed metal bellows, may be employed and suitably attached in the piston forming in effect a bladder.

It should not be understood from the foregoing that the` cylinder I2 necessarily constitutes a portion of the casing II for obviously the cylinder I2 may be of somewhat smaller diameter than the diameter of the casing II and attached to the bottom thereof in conventional manner. However, if a separate cylinder is to be cmployed, a modified form of my pump illustrated in Figures 4 and 5A can be used.

In this modication, a pump cylinder l5I is adapted for threaded engagement with the lower end of casing II and is provided with a well point I3 similar to that previously described. The cylinder 5I is, of course, of such conguration which may be engaged by a rod or probe introduced into the casing II from the surface for removal and when so removed will carry with it the hollow piston I8 and its associated parts. The bore of the pump cylinder 5I is eccentric to its exterior thereby forming a relatively thick wall section 52 on one side in which an air duct 53 may be formed extending from the upper end of` the cylinder-'5I downwardly to a point below the hollow piston I8, at which point it communicates with the bore. The upper end of the air duct 53 is threaded to engage an air supply pipe 54 which extends to the surface and comvious that the location of the power piston and its accompanying source of power with respect to the well is immaterial since the connecting pipe 3l may'be of substantially any length Without materially interfering withthe eillciency of the pump. To illustrate the practical application of this advantage, the engine and power piston may, for example, be located in the basement of a house and communicate by a pipe with a well located at some relatively remote point thereby permitting accessibility to the pump engine and providing the necessary shelter. Similarly, if

' the pumping apparatus is to be driven by a windmill, the well may be driven in a hollow and connected by pipe to a power piston on the windmill which may be disposed on the top of a hill some distance removed from the well to take full advantage of the wind.

The cost of construction of my pump is un- L usually low since it will be noticed that only a minimum number of valves are employed with few moving parts .and the component parts required are of simple shapes which may be easily fabricated from inexpensive material at low cost. Lifting rods which are often a source .of difiiculty in conventional pumps are completely eliminated. My pump is obviously adapted for use in either shallow or deep wells and in other situations, for example, where liquid is moved from a low pressure tank to a high pressure tank, although maximum advantage of my pump will be realized when employed in deep wells such as are often encountered in the pumping of petroleum and water.

The unique means provided for separating a charge of gas in the hollow piston from the liquid being pumped substantially eliminates any potential failure of the pump which would normally require removal of the piston from the well. The viscosity of the liquid employed does not present any particular diiculty except that viscous liquids Will require proportionately larger valve openings and is the case with liquids having a viscosity equal to or less than that of water. Furthermore, when employed in deep wells where the temperature is relatively constant, it will be found that in operation the quantity of liquid delivered by my pump is substantially constant in proportion to the number of strokes of the power piston and that as a result may be employed as an approximate gauge or measure of the liquid pumped.

In compliance with R. S. 4888, I have herein described a specific embodiment of my invention but it is to be understood that this disclosure hasA been made for illustrative purposes only and is not to be understood as a limitation of my invention to the precise details herein contained exce'pt in so far as defined in the appended claims.

I claim:

1. Pumping apparatus adapted for use with a casing communicating with a liquid supply comprising a cylinder communicating with the casing and disposed adjacent the liquid supply,

a piston reciprocably mounted in the cylinder, irreversible means for admitting liquid to the cylinder below the piston, resilient means acting on the piston for neutralizing the static pressure of the liquid in the casing against the piston, irreversible liquid inlet and outlet means on the piston, means for trapping a body of gas within the piston, means for maintaining gas within the piston and means communicating with the casing above the piston forl varyingv the static pressure of the liquid in the casing against the piston whereby the piston is reciprocated in the cylinder to produce pumping action.

2. Pumping apparatus adapted for use with a casing communicating with a liquid supply comprising a cylinder communicating with the casing and disposed adjacent the liquid supply,

a piston reciprocably mounted in the cylinder, ir-

reversible means for admitting liquid to the cylinder below the piston, resilient means acting on the piston for neutralizing the static pressure of the liquid in the casing against the piston, irreversible inlet means and, irreversible outlet means in the piston, means for trapping a body of gas within the piston, movable means within the piston separating said body of gas from liquid, and means communicating with the casing above the piston for varying the static pressure of the liquid in th'e casing against the piston whereby the piston is reciprocated in the cylinder to produce pumping action.

3. Pumping apparatus adapted for use with a casing communicating with a liquid supply comprising a cylinder communicating with the casing and disposed adjacent the liquid supply, a piston reciprocably mounted in the cylinder, sealing means for preventing the passage of liquid between the piston and the cylinder irreversible means for admitting liquid to the cylinder below the piston resilient means for urging the piston upwardly against the static pressure of the liquid in the casing against the piston, irreversible inlet means in the piston, irreversible outlet means in the piston above the sealing means, a gas chami ber within the piston, means for maintaining a volume of gas within the chamber and means communicating with the casing above the piston for varying the static pressure of the liquid in the casing against the piston whereby the piston is reciprocated in the cylinder to produce pumping action.

4. Pumping apparatus adapted for use with a casing communicating with a liquid supply comprising a cylinder communicating with the casing and disposed adjacent the liquid supply, a piston reciprocably mounted in the cylinder, a spring for urging the piston upwardly, irreversible inlet means in the piston, irreversible outlet means in the piston, means for trapping a body of gas within the piston including ,a tube extending upwardly from a point within the piston, movable means within the piston separating the body of gas from the liquid, and means communicating with the casing above the piston for varying the static pressure of the liquid in the casing against the piston whereby the piston is reciprocated in the cylinder to produce pumping action.

5. Pumping apparatus adapted for use with a casing communicating with a liquid supply comprising a cylinder communicating with the casing and disposed adjacent the liquid supply, arpiston reciprocably mounted in the cylinder, irreversible means for admitting liquid to the cylinder below the piston, resilient means acting on the piston asador? for neutralizing the static pressure of the liquid in the casing against the piston, irreversible inlet means in the piston, irreversible outlet means in the piston, means for trapping a body of gas within the piston including a tube extending upwardly from a point within the` piston, a iloating piston telescoped over the tube in sealing reciprocable relation therewith and with said first mentioned piston for separating the gas from the liquid, and means communicating with the casing above the piston for varying the static pressure of the liquid in the casing against the piston whereby the piston is reciprocated in the cylinder to produce pumping action.

6. Pumping apparatus adapted for use with a casing communicating with a liquid supply comprising a cylinder communicating with the casing and disposed adjacent the liquid supply, a piston reciprocably mounted in the cylindenirreversible means for admitting liquid to the cylinder below the piston,` resilient means acting on the piston for neutralizing the static pressure of the liquid in the casing against the piston, irreversible inlet means in the piston, irreversible outlet means inthe piston, means for trapping a body of gas Within the piston at superatmospheric pressure, movable means within the piston separating said body of gas from liquid, and means communicating with the casing above the piston for varying the static pressure of the liquid in the casing against the piston whereby the piston is reciprocated in the cylinder to produce pumping action.

7, Pumping apparatus adapted for use with a casing communicating with a liquid supply comprising a cylinder communicating with the casing and disposed adjacent the liquid supply, a piston reciprocably mounted in the cylinder, irreversible means for admitting liquid to the cylinder below the piston, resilient means for neutralizing the static pressure of the liquid inthe casing against the piston, irreversible inlet means in the base of the piston, irreversible outlet means in the piston above the inlet means, means for trapping a body of gas within the piston, means comprising a gas valve communicating with the body of gas and the exterior of the piston for introducing compressed gas, movable means within the piston for separating the gas'from the liquid, and means communicating with the casing above the piston for varying the static pressure of the liquid in the casing against the piston whereby the piston is reciprocated in the cylinder to produce pumping action.

8. Pumping apparatus adapted for use with a casing communicating with a liquid supply comprising a cylinder communicating with the casing and disposed adjacent the liquid supply, a piston reciprocably mounted in the cylinder, irreversible means for admitting liquid to the cylinder below the piston, resilient means acting on the piston for neutralizing the static pressure of the liquid in the casing against the piston, irreversible liquid `inlet and outlet means on the piston, means comprising a ilexible diaphragm for trapping a body of gas within the piston, and means communicating with the casing above the piston for varying the static pressure of. the liquid in the casing against the piston whereby the piston is reciprocated in the cylinder to produce pumping action.

9. Pumping apparatus adapted for use with a casing communicating with a liquid supply comprising a cylinder communicating ywith the casing and disposed adjacent the liquid supply, a piston reciprocably mounted in the cylinder! irreversible means for admitting liquid to the cylinder below the piston, resilient means acting on the piston for neutralizing the static pressure of the liquid in the casing against the piston, irreversible liquid inlet and outlet means on the piston, means including a bladder within the piston for trapping a body of gas within the piston, and means communicating with the casing above the piston for varying the static pressure of the liquid in the casing ,against the piston whereby the piston is reciprocated in the cylinder to produce pumping action.

10. Pumping apparatus adapted for use with a casing communicating with a liquid supplt,r comprising a cylinder communicating with Vthe casing and disposed .adjacent the liquid supply, a piston reciprocably mounted in the cylinder, irreversible `means for admitting liquid to the cylinder below the piston, resilient means acting on the piston for neutralizing the static pressure of the liquid in the casing against the piston, irreversible liquid inlet and outlet means on the piston, means including a metal bellows within the piston for trapping a body of gas within the piston, and means communicating with the casing above the piston for varying the static pressure of the liquid in the casing against the piston whereby the piston is reciprocated in the cylinder to produce pumping action.

11. Pumping apparatus adapted for use with a. casing communicating with a liquid supply comprising a cylinder communicating with the casing and disposed adjacent the liquid supply, a piston reciprocably mounted in the cylinder, irreversible means for admitting liquid to the cylinder below the piston, resilient means associated with the piston for neutralizing the static pressure of the liquid in the casing against the piston, irreversible liquid inlet and outlet means on the piston, means including a bladder for trapping a body of gas within the piston, a tube extending from a point within the piston to said outlet means, and means communicating with the casing above the piston for varying the static pressure of the liquid in the casing against the piston whereby the piston is reciprocated in the cylinder to produce pumping action. l

12. Pumping apparatus adapted for use with a casing communicating with a liquid supply comprising a cylinder communicating with the casing and disposed adjacent the liquid supply, a piston reciprocably mounted in the cylinder, irreversible means for admitting liquid to the cylinder below the piston, resilient means acting on the piston for neutralizing the static pressure of the liquid in the casing against the piston, irreversible liquid inlet and outlet means on the piston, means including a bladder for trapping a body of gas within the piston, a perforated tube extending from a point within the piston to said outlet means, and means communicating with the casing above the piston for varying the static pressure of the liquid in the casing against the piston whereby the piston is reciprocated in the cylinder to produce pumping action.

13. A piston for use in a liquid pumping apparatus of the type described comprising a hollow cylinder having openings to receive irreversible liquid inlet and outlet means, means within the cylinder for trapping a body of gas, and movable means for separating the body of gas from the liquid.

14. Pumping apparatus adapted for use witlra casing communicating with a liquid supply comprising a cylinder communicating with the casing accada? and disposed adjacent the liquid supply, a piston reciprocably mounted in the cylinder, irreversible means for admitting liquid to the cylinder below the pistoesilient means acting on the piston for neutralizing the static pressure of the liquid in the casing against the piston, irreversible liquid inlet and outlet means on the piston, means for trapping a body of gas within the-piston, means for maintaining the volume of said body of gas during the operation of the piston, and means communicating with the casing above the piston for varying the staticpiessure of the liquid in the casing against the piston whereby the piston is reciprocated in the cylinder to produce pumping action.

15. Pumping apparatus adapted for use with a casing communicating with a liquid supply comprising a cylinder communicating with the casing and disposed adjacent the liquid supply,

. a piston reciprocably mounted in the cylinder, ir-

reversible means for admitting liquid to the cylinder below the piston, resilient means acting on the piston for neutralizing the static pressure of the liquid in the casing against the piston, irreversible liquid inlet and outlet means on the piston, means for trapping a body of gas within the piston, means for maintaining volume of said body of gas above a predetermined minimum volume including a gas supply conduit communicating with the cylinder below the piston and with a supply of compressed gas, and means communicating with the casing above the piston for varying the static pressure of the liquid in the casing against the piston whereby the piston is reciprocated in the cylinder to produce pumping action.

16. Pumping apparatus adapted foruse with a casing communicating with a liquid supply comprising a cylinder communicating with the casing and disposed adjacent the liquid supply, a piston reciprocably mounted in the cylinder, irreversible means for admitting liquid to the cylinder below the piston, resilient means associated with the piston for nutralizing the static pressure of the liquid in the casing against the piston, irreversible liquid inlet and outlet means on the piston, means for trapping a body of gas within the piston, means for maintaining the volume of said body of gas above a predetermined minimum including a quantity of material within the piston adapted to generate gas by reaction f of the liquid being pumped, and means communicating with the casing above the piston for varying the static pressure of the liquid in the casing against vthe piston whereby the piston is reciprocated in the cylinder to produce pumping action;

17. Pumping apparatus adapted for usefwith a casing communicating with the liquid supply comprising a cylinder communicating with the casing and disposed in the liquid supply, a hollow piston reciprocably mounted in sealed relation with the cylinder a check valve for admitting liquid to the 'cylinder below the piston, an inlet check valve carried by the hollow piston, spring means within the cylinder positioned betweenfor maintaining gas in said chamber, and means including a power piston communicating with the casing above the hollow piston forA varying the static pressure of the liquid in the casing against the hollow piston whereby liquid is forced through the hollow piston and into the casing by reciprocatlon oi the power piston.

18. Pumping apparatus adapted for use with a casing communicating with a liquid supply comprising a cylinder communicating with the casing and disposed in the liquid supply, a hollow piston reciprocably mounted in sealed relation with the cylinder, a check valve for admitting liquid to the cylinder below the piston, an inlet check valve in the hollow piston, an outlet check valve in the piston, spring means Within the cylinder acting on the piston for neutralizing the static pressure of liquid in the casing against the piston, means for trapping a body of gas within the piston means for maintaining the volume of the gas body in the piston, outlet means communicating with the casing above the cylinder including a preloaded outlet check valve, and means including a power piston communicating with the casing above the piston for varying the static pressure of the liquid in the casing against the piston whereby liquid is forced through the piston and into the casing by reciprocatlon of the power piston.

19. Pumping apparatus, comprising a cylinder, a piston reciprocably mounted in the cylinder, spring means acting on the piston to resiliently resist downward pressure on the piston, a chamber in the piston wherein gas may be trapped and compressed, an irreversible inlet to the piston, an irreversible outlet from the piston, a gas supply port carried by the cylinder-piston assembly for introducing gas into the gas chamber, and an irreversible inlet to the cylinder below the piston,

20. Pumping apparatus, comprising a cylinder, a piston reciprocably mounted in the cylinder, spring means acting on the piston to resiliently resist downward pressure on the piston, a chamber in the piston wherein gas may be trapped and compressed, an irreversible inlet to the piston, an irreversible outlet from the piston, and means for maintaining the desired volume of gas in said gas chamber comprising a conduit leading to the cylinder-piston assembly whereby gas may be introduced into said chamber.

' 21. Pumping apparatus comprising a cylinder, a piston reciprocably mounted in the cylinder, spring means acting on the piston to resiliently resist downward pressure on the piston, a chamber in the piston wherein gas may be trapped and compressed, an irreversible inlet to the piston, an irreversible outlet from the piston, and means for maintaining the desired volume of gas in said gas chamber, 'comprising a. gas supply port communicating with the cylinder below the piston and with a supply of compressed gas.

ARNOLD S. SOBERG.

REFERENCES CITED The following references are of record in the ille of this patent:

UNrrED STATES PATENTS Number Name Date 2,126,880 Gardner Aug. 16, 1938 2,238,809 Hall et al Apr. l5, 1941 

